I am not especially familiar with any of the many commercial miticide treatments that are available, and so make no comment about PROmite or any other product.
Mites have been living with humans for thousands of years and have so far resisted everything we have tried to get rid of them!
The mite population thrives in warm and humid conditions - hence their love of beds! I am generally against the widespread use of of miticides and insecticides in the home, they do have their uses, of course, for control of massive populations and in acute situations.
Most of those who are concerned about these creatures are already suffering with a sensitivity or even an allergic reaction to the mites' faeces - these are the very people I would be very wary of exposing to any pesticide at all, let alone their bed where they will be spending 8 hours a night in close contact to your chemicals!
My advice would be to explain that the best control method is good hygiene - including airing the bedroom, bedding and regular vacuuming of all areas including mattresses with a very good quality vacuum and HePa filters. If the infestation has been quite high then the use of steam and vacuum by a professional cleaning company will reduce the burden to manageable levels - ensuring that the area is properly dry after cleaning etc.
There is no easy solution if people will not reduce the humidity and warmth of the environment during the day, whether you use a pesticide or not.
I also recommend that you and your staff read and understand the MSDS information on any pesticide that you use, you will be exposed to potentially high dose levels during application if safeguards are not used, and these may themselves lead to skin, eye or respiratory reactions themselves.
Good Luck.